A variety of procedures, methods or machines are known in agriculture for dispensing or distributing of seeds and fertilizer in granular form in a most even way on a farmland area. One kind of these machines is called a seed singulating machine. In the case of seed singulating machines, it is possible to single out grains by means of metering devices and to place these in regular intervals into a seed furrow. Generally, the seed furrow is produced by means of appropriate furrowing tools. In this way, almost all the seeds are provided with about the same growing space, which ensures a uniform development of the plants.
In addition to the growing space, the selection of the best suited seeds for the respective location is also crucial for the development of the plants. For example, there are some kinds of seeds that are better suited for rather dry and others for moist soil conditions. Some kinds of seeds are also better suited for heavy clay-like soils and others for rather light sandy soils. But since the soil conditions can often be varied, in particular in the case of fields that cover a large area, it would be advantageous if the kinds of seeds could be adapted within the field according to the respective soil condition.
A variety of approaches to solve this are known from prior art. U.S. Pat. No. 6,672,228 B1, for example, describes a metering system for a row unit, wherein the metering system consists of two metering devices. For example, by means of a carousel, it is possible to supply different kinds of seeds to the respective metering devices. After separating the seeds, the individual grains are placed in a seed pipe so that the seeds can be transported into the seed furrow. When there is a change of the seeds dispensing into the seed pipe from the first metering device to the second metering device, these can be respectively moved in an axial direction by means of a slider. The device is characterized in that when individual seed dispensing is performed in the first metering device, the second metering device does not perform any separation or vice versa, which means that only one respective metering device is active at a time.
Although it is thus possible to dispense different kinds of seeds, the moving of the metering device and of the carousel makes a quick change between the two metering devices or between the different kinds of seeds impossible. At faster driving speeds and frequent changes of seeds, it is possible that there are inaccuracies in the seed dispensing due to the time that is necessary for changing of the metering devices. The design of the row unit with slider and carousel is also often very extensive and thus also correspondingly costly. Furthermore, there is a problem with the seed dispensing because it occurs in the seed pipe in a free fall. Due to vibrations and impacts which can occur in the row unit during driving in the field, it is possible that the seeds are misplaced within the seed pipe or that the seeds collide within the seed pipe. This can also result in an uneven grain dispensing.
Another metering device by means of which seeds can be dispensed in a metered or individual manner is known from U.S. Pat. No. 7,765,943 B2. In this device, the seeds can be volumetrically metered by means of a rotary valve or it can be separated by means of a metering unit. The supply of the seeds is regulated by a slide, whereby either a volumetric metering or a separation of the seeds is performed, depending on the position of the slide.
A further agricultural machine with two metering devices has been known through the US-based company “Kinze Manufacturing Inc.”. In their so-called Multi-Hybrid Planter 4900, two metering devices comprise one common seed dispensing area. The metering devices are operated by means of low pressure systems respectively. After the grains are dispensed from one metering unit, they are placed into the seed furrow by means of a free fall through a seed metering pipe. The switching between the metering devices or the kinds of seeds is performed, for example, by means of GPS-data. Yet, low pressure metering devices have the disadvantage that they are very susceptible to dirt. In particular, dirt particles can be sucked in by means of the low pressure in the metering device, which can lead to malfunctions.
From WO 2014 113 803 A1, a further metering system for a row unit is known. This metering system can be supplied with at least two different kinds of seeds, whereby only one kind of seed can be dispensed with the respective metering device. However, this system has the disadvantage that a quick switching between the kinds of seeds is not possible because there is only one metering device. Rather, a respective waiting-time must be defined, in order to take into account the time that is required for the grains to reach from the central seed tank to the metering device. But such a system is very complex and it is also error-prone if the timings are not chosen correctly.
Another metering system is known from WO 2014/205454 A1, which comprises two metering devices. The two metering devices are arranged with a distance between each other and both use the vacuum principle. It is thus possible that the seeds can be accommodated by the cut-outs of the metering elements. The seeds that are captured by the cut-outs can then subsequently fall into one common seed metering pipe or into two separate seed metering pipes by means of gravity.
Other systems are also known from prior art, in which two streams of seeds are connected by means of a Y-piece, whereby these are generally metered volumetrically. Also, a connection of the streams of seeds is not yet synchronized, which means that single grain dispensing cannot be guaranteed. It is also already known that, for example, micro granules are added into a stream of individual grains. Up to now, a separated grain dispensing of these two compounds can also not be guaranteed in this case. Additionally, the stream of individual grains can possibly be affected, by means of which a sufficiently accurate seed dispensing can no longer be ensured.